Antacids generally available are of the insoluble type which function by raising the pH of the stomach to a desired value, between 4 and 5, and maintaining this pH for some period.
Insoluble antacids depend on surface area (particle size) for their efficiency. The smaller the particle size, the larger the surface area--thus more contact between acid to be neutralized and neutralizer. It is generally accepted that liquid antacids are superior to tabletted products due to increased surface area and wettability. A liquid product offers the benefit of an insoluble antacid which is milled to a fine particle size and completely wetted to provide prompt activity in the stomach. However, liquids in the form of suspensions or emulsions, while not gritty, possess organoleptic deficiencies, causing many manufacturers to suggest co-ingestion of milk or water to alleviate symptoms of the onset of nausea.
A chewable tabletted product, moreover, requires the user to mascerate the mass with his teeth but still not attaining the small particle size and uniformity present in the liquid. Tabletted antacid products, however, offer the user convenience over the liquid--these products are more portable and contain accurate dose forms without the need for a measuring device such as a teaspoon.
Palatability and "mouth feel" are also extremely important factors in formulating antacids. Conventional metallic carbonate and hydroxide insoluble antacid materials usually have both an unpleasant mouth feel and an unpalatable taste due to chalkiness, grittiness, dryness and astringent properties of these materials. Accordingly, the practical value of these antacid materials is substantially diminished since patients finding them objectionable may fail to take them as prescribed.
In an effort to overcome the above problems, flavorings, such as peppermint oils, have been employed with antacids. Unfortunately, it has been found that the flavoring merely masks the unpleasant taste, but the chalkiness, grittiness, dryness and astringent properties still remain.
It has also been suggested to coat antacid tablets with a coating material which will not dissolve in the saliva so that it masks the disagreeable taste and mouth feel and will dissolve in the stomach. However, it has been found that most coatings suggested for such use dissolve in the intestines and not the stomach and thus provide the antacid at the wrong site. Moreover, although the coating may dissolve in the stomach, the rate of dissolution may not be fast enough to allow for sufficient neutralizing reaction time of the antacid with gastric acid before the antacid is removed from the stomach by gastric emptying.
U.S. Pat. No. 3,843,778 to Diamond et al. discloses a technique for coating antacid particles with a water insoluble, inert, non-toxic hydrocarbon oil which is formulated into suspensions or tablets which are said to be substantially free of the impalatable "mouth feel" properties associated with antacids. An electro-negative agent, such as a surfactant selected from an alkyl aryl sulfonate, or an alkyl sulfate or sulfonate, or sulfonated amides or amines; or sulfated or sulfonated esters or ethers, or a dioctyl sulfosuccinate, or a hydrated aluminum silicate, such as bentonite or kaolin, is employed to aid in adhering the oil to the electropositively charged antacid particles.
U.S. Pat. No. 3,253,988 to Scott discloses an orally administrable antacid formed of oils or fats, that is esters of higher fat acids and a trihydric alcohol, in combination with antacids. The Scott antacid may be in the form of a waxy solid, an emulsion or suspension.